Patent PT-1828697-E (PT)
Title: Method and installation for producing treated natural gas from a c3+ hydrocarbon-rich cut and ethane-rich stream
Inventor: PARADOWSKI HENRI
IPC: F25J3/00
Filed: 2005-12-19
Abstract: The simultaneous production of treated natural gas (I) from an initial natural gas (II), a fraction (H1) rich in C 3 +> hydrocarbons with and, in some production conditions, a stream (S1) rich in ethane comprises: cooling and condensing (II) partially; separating the cooled natural gas (III) into a liquid stream (S2) and a gas stream (S3); diluting and introducing (S2) into a recuperation column (VI); separating; expanding; cooling and condensing; recovering top and bottom streams; introducing a first reflux stream; and tapping. The simultaneous production of treated natural gas (I), a fraction (H1) rich in C 3 +> hydrocarbons and, in some production conditions, a stream (S1) rich in ethane) from a starting natural gas (II), comprising methane, ethane and C 3 +> hydrocarbons, comprises: (a) cooling and condensing (II) partially; (b) separating the cooled natural gas (III) into a liquid stream (S2) and a gas stream (S3); (c) diluting and introducing (S2) into a recuperation column (VI) of hydrocarbons with C2+ at a first intermediate level (N1); (d) separating (S3) into a stream (S4) feeding the column and a reflux stream (S5); (e) expanding (S4) in a turbine (A1) and introducing it into (VI) at the second intermediate level (N2); (f) cooling and condensing (S5) partially and, after expansion, introducing it into (VI) at a third intermediate level (N3); (g) recovering the top stream (S6) of (VI) to form the treated and recovering the bottom stream (S7) of (VI) to form a liquid stream rich in hydrocarbons with C2+; (h) introducing (S7) at a supply level (P1) of a fractionating column (F1) provided with a top condenser (E1), where (F1) producing a stream (S8) rich in ethane (on top) and (H1) (at the bottom); (i) introducing a first reflux stream (S9) produced in (E1) in reflux in (F1); (j) and tapping (S8) from an intermediate level (P2) of (F1) located above (P1) of (61). When rates of extraction of ethane lower is than a predetermined threshold, a secondary reflux stream (S10) from (E1) is produced and introduced in reflux at the top of (VI). An independent claim is also included for the installation for the above process, comprising: (i) means of cooling and partial condensation of (II); (ii) means of separation of (III) to (IV) and (S2); (iii) a column (VI) of recuperation of hydrocarbons with C2+; (iv) means of dilution and introduction of (S3) into the column of recuperation, opening into (N1) of (VI); (v) means of separation of (S2) to form a stream supplying (VI) and (S5); (vi) a turbine (A1) for expansion of (S4) and means of introduction of the stream from (A1) to (N2) of (VI); (vii) means of cooling and condensation at least partial of (S5), opening into the means of expansion of the cooled reflux stream; (viii) means of introduction, at (N3) of (VI), cooled reflux stream coming from the means of expansion of the cooled reflux stream; (ix) means recuperation of the top column stream to form (I); (x) means of recuperation of the bottom column stream to form a liquid stream rich in hydrocarbons with C2+; (xi) a fractionating column (F1) provided with a top condenser (E1); (xii) means of introduction of (S7) at (P1) of (F1); (xiii) means of recuperation of (S1), located at the head of (F1), and the means of recuperation of (H1) located at the bottom of (F1); (xiv) and means of introduction of a first reflux stream produced (E1) as reflux in (F1). The means of recuperation of (S1) are at (P2) of (F1) located above (P1) of (F1). The installation comprises means of production, for rates of extraction of ethane from the natural starting gas lower than a predetermined threshold, (S10) coming from (E1) and means of introduction of (S10) into the recuperation column (VI).